Nuclear reactor

Abstract

.Iadd.A nuclear reactor with control rods in channels between fuel assemblies wherein the fuel assemblies incorporate guide rods which protrude outwardly into the control rod channels to prevent the control rods from engaging the fuel elements. The guide rods also extend back into the fuel assembly such that they are relatively rigid members. The guide rods are tied to the fuel assembly end or support plates and serve as structural members which are supported independently of the fuel element. Fuel element spacing and support means may be attached to the guide rods..Iaddend.

We claim: 
     
       1. A core for a nuclear reactor comprising a plurality of longitudinally extending generally parallel fuel elements, said fuel elements being grouped into a plurality of fuel element assemblies and control rods interposed between certain of said fuel element assemblies, said fuel element assemblies adjacent said control rods .Iadd.each .Iaddend.including .Iadd.a pair of spaced laterally extending support plates with said fuel elements being supported between said support plates and within the confines of a laterally extending polygon and further including longitudinally extending .Iaddend.guide rods .[., said guide rods extending.]. generally parallel .Iadd.and of a length coextensive .Iaddend.with said fuel elements .Iadd., said guide rods supported between said spaced support plates independently of said fuel elements and arranged in said assembly .Iaddend.with a .Iadd.first .Iaddend.portion .[.of said guide rods.]. .Iadd.thereof .Iaddend.extending .[.outwardly from the fuel elements grouped in said assemblies.]. .Iadd.outside of said polygon throughout the length of said guide rods .Iaddend.towards said control rods whereby said guide rods will prevent said control rods from engaging said fuel elements .Iadd.and a second portion thereof extending inside of said polygon throughout the length of said guide rods, said guide rods thereby having a lateral dimension extending from outside said polygon to inside said polygon such that said guide rods are relatively rigid structural members. .Iaddend. 
     
     
       2. A core for a nuclear reactor as recited in claim 1 .[.wherein the lateral cross section of said fuel element assemblies comprises a polygon.]. and further including fuel element spacing and support means intermediate the ends of said fuel elements, said spacing and support means being affixed to said guide rods whereby said spacing and support means will be maintained in position. 
     
     
       3. A nuclear fuel element assembly comprising .Iadd.a pair of spaced laterally extending support plates, .Iaddend.a plurality of longitudinally extending, generally parallel fuel elements .Iadd.supported between said support plates .Iaddend. and at least one longitudinally extending guide rod generally parallel and .Iadd.of a length .Iaddend.coextensive with said fuel elements, said fuel elements arranged in said assembly within the confines of a laterally extending polygon, said guide rod .Iadd.extending between said spaced support plates and supported independently of said fuel elements and .Iaddend.arranged in said assembly with a .Iadd.first .Iaddend.portion thereof extending outside of said polygon throughout the length of said guide rod .Iadd.and a second portion thereof extending inside of said polygon throughout the length of said guide rod, said guide rod thereby having a lateral dimension extending from outside said polygon to inside said polygon such that said guide rod is a relatively rigid structural member .Iaddend.and further including a fuel element spacing and support means intermediate the ends of said fuel elements, said means including a band extending laterally around the outside of said fuel elements and defining said polygon, said band having a portion removed, a portion of said guide rod extending through said removed portion so as to extend beyond the outside of said band. 
     
     
       4. A core for a nuclear reactor comprising a plurality of longitudinally extending fuel element assemblies, said fuel element assemblies spaced apart to provide control rod channels therebetween, said fuel element assemblies each comprising .Iadd.a pair of spaced laterally extending support plates, .Iaddend.a plurality of longitudinally extending, generally parallel fuel elements .Iadd.supported between said support plates .Iaddend.and at least one longitudinally extending guide rod generally parallel to and coextensive with said fuel elements .Iadd.and supported independently of said fuel elements, .Iaddend.said fuel elements arranged in said assemblies within the confines of laterally extending polygons, and said guide rods arranged in said assemblies with a portion of each of said guide rods extending outside of said polygons and into said control rod channels substantially throughout the length of said guide rods thereby providing control rod guide surfaces extending outwardly from said fuel element assemblies .Iadd.and with another portion of each of said guide rods extending inside of said polygons whereby said guide rods have a lateral dimension extending from outside said polygons to inside said polygons such that said guide rods are relatively rigid structural members. .Iaddend. 
     
     
       5. A core for a nuclear reactor as recited in claim 4 wherein each of said fuel element assemblies includes a plurality of said guide rods with at least one guide rod on each side of said polygon. 
     
     
       6. A nuclear fuel element assembly as recited in claim .[.5.]. .Iadd.9 .Iaddend.wherein said band is attached to said guide rod whereby said fuel element spacing and support means will be maintained in position. 
     
     
       7. A core for a nuclear reactor as recited in claim 4 wherein said fuel elements and said guide rods have generally circular cross sections of approximately equal size and wherein said portions extending outside said polygons comprise longitudinally extending bars affixed to said guide rods. 
     
     
       8. A core for a nuclear reactor as recited in claim 4 wherein said fuel elements and said guide rods have generally circular cross sections and wherein the cross sections of said guide rods are larger than the cross sections of said fuel elements and wherein said portions extending outside said polygons comprise longitudinally extending segments of said guide rods. 
     
     
       9. A core for a nuclear reactor as recited in claim 8 and further including fuel element spacing and support means intermediate the ends of said fuel elements, said spacing and support means including bands extending laterally around the outside of said fuel elements and defining said polygons, said bands having portions removed, and said longitudinally extending segments of said guide rods extending through said removed portions so as to extend beyond the outside of said bands.